Electric slip-ring and brush connection



Oct. 19, 1948.

E. KNUDSEN ELECTRIC SLIP RING AND BRUSH CONNECTION Filed Aug. 28, 1946 MHH m n W n 3 l'rlz'ng .JLKrz udselz (Qu; PM

Patented t. 19, 1948 amass ELECTRIC SLIP-RING AND BRUSH CONNECTION M. Knudsen, Arlington, N. 1., assignor to Curtiss-Wright Corporation, Dela were a corporation of Application August 28, 1946, Serial No. 693,590

7 Claims.

tiometers having contacts rotatable in either direction on a circular resistance card for example, in thecircuits or electric computing and integrating systems such as flight computing circuits oi grounded aircraft trainers, involves the problem of providing a low resistance connection at the slip-ring or equivalent connections and also precluding variation in resistance in order that precision of the apparatus be not impaired. This is particularly the case where the slip-ring and brush construction is necessarily simple and inexpensive and comparatively high contact pressure is required. For example, a slip-ring connection of this type may rotate in a definite direction to give smooth operation and substantially'constant low electrical resistance. When however the apparatus is rotated in the opposite direction vibration or chattering of the brush may result causing material and objectionable variations in the slip ring resistance. Such variation in. resistance mays'eriously impair the accuracy of the computing system.

A'principal object of this invention therefore is to provide improved electric slip-ring and brush connections for electrical apparatus Of the character abovereferred to that is simple, rugged and inexpensive in construction, and that is capable of maintaining good electrical contact without objectionable variation in resistance during. continuous or intermittent rotation in either direction. v A further and more specific object of this invention is to provide an improved vibration-free,

wire type brush and mounting structure there for arranged so as to utilize the resiliency of the brush for looking it in operating position, thereby eliminating the necessity for clamps, set screws,

and the like, and that facilitates ready and easy removal and replacement of an individual brush particularly where used in a multiple slip-ring and brush assembly.

The invention will be more fully set forth in the following description referring to the accompanying drawing, and the features. of novelty will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a sectional view of potentiometer apparatus to which the present invention is applied;

Fig. 2 is an enlarged view partly in section of the slip-ring and brush connection embodying the present invention, and

,Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2.

The potentiometer apparatus illustrated by way of example in Figure 1 is of the type used in electrical computing systems wherein a plurality of potentiometers generally indicated at I, 2, 3 and 4 respectively are operated in unison from a common shaft 5 that may be connected through a drive shaft gear 6 and driving pinion 1 to a servo-motor or the like, the operating shaft of which is indicated at 8. The apparatus is mounted within a cylindrical housing 9 having a partition In for supporting the potentiometers and serving as a bearing support for the shaft 5. An extension H of the housing is also provided with a partition [2 in which the servo-shaft 8 may be journalled, this partition defining with the partition I 0 a. gear housing as illustrated.

Each potentiometer comprises a cylindrical insulating member i3 concentrically mounted with respect to the shaft 5 on the partition I0 and secured thereto by screws I 3'. A resistance element or card I 4 that may be wound for linear, sinusoidal or other resistance characteristics as the case may be, is wrapped around the outer surface Of the cylindrical member and is secured thereto so that the contact edge of the resistance element extends slightly beyond the outer edge of the insulating member. This edge of the resistance element is engaged by a movable contact i 5 that is carried by an insulating member l6 secured to the shaft 5 by means of a retaining collar ii for rotation therewith. The shaft 5 carrying the movable contact assembly is supported within a hub-like extension I! of the partition iii in the bearings l8 and IS.

The terminals l5 of the movable contacts 15 are electrically connected to fixed external circuits through the improved multiple slip-ring and brush assembly generally indicated at 20 in a manner presently described. The slip-ring stack is mounted on the hub extension I! and comprises a plurality of conducting disc-like sliprings 2| that are separated by insulating discs or spacers 22, the assembly being insulated from the extension by an insulating sleeve 23 and positioned between a hub shoulder 24 and a washer 25' and retaining nut 25 secured to the extension. Alined apertures 26 in the slip-rings and spacing discs are provided for the conductor leads such as the conductor 21, that connect the individual slip-rings by a soldered connection, as at 26, Figs. 1 and 3, to external circuits. The terminals of the potentiometers being fixed are connected to the external circuits in any suitable manner by conductors (not shown). The coacting brushes 28 for the respective slip-rings arecarried by and rotatable with the contact member l6 and are electrically connected to the respective contacts IS in a suitable manner by conductors, such as indicated at 29, Figs. 1 and 2.

Referring to Figs. 2 and 3 each individual slipring and brush assembly comprises a conducting ring 2| and brush 28 above referred to, that are related to each other so that the ring 2i, or the brush 28 as the case may be, can rotate with respect to the other in either direction without vibration at the contact surfaces. The outer peripheral edge of the ring 2| has formed therein a notched or V-shaped groove 2i, the apex of which points toward the center of the ring. The brush 28 is formed in a, manner presently described of a conductingmetal strip or wire that bears in the groove M in a. direction generally tangential to the disc periphery and is under an initial tension for resiliently locking the brush in position and for applying proper contact pressure at the conducting surfaces.

I have found that the brush can be resiliently mounted without the usual fastening screws and that vibration can be eliminated and smooth operation obtained when the ring is rotated in either direction by the construction shown specifically in Fig. 2 wherein the wire constituting the brush is generally of scythe shape and is resiliently and snugly supported at a point intermediate the brush terminal post and the part that makes contact with the slip-ring. The brush terminal support 30 is adjacent to the ring and has a bore in which the ofiset terminal end 28a of the brush is inserted so that it is restrained with respect to transverse movement. The contact portion 28 and the offset terminal portion are generally in the same plane as shown. The terminal support is of insulating material and is mounted on and carried by the rotatable member I6 so that it extends substantially parallel to the axis of the slip-ring assembly, 1. e. parallel to shaft 5. The brush extends from this support toward a relatively fixed positioning post 3| of insulating material spaced a, short distance therefrom and having a plurality of longitudinally spaced annular grooves 32 for accommodating the individual brushes respectively as indicated in Fig. 1.

For the purpose of resiliently and firmly locking the brush in position with respect to the terminal support and positioning post without the use of clamps, screws and similar fastening means, the post is located substantially in alinement with the brush portion 28a so that the brush must be moved laterally and stressed in order to pass by the post. This causes the brush to press firmly against the post. The brush is-also suitabl shaped so that it clings to the post as it is resiliently biased against it, thereby tending also to restrain the brush terminal portion with respect to longitudinal movement.

Specifically, the brush is formed with a U-shaped bend 2% that fits snugly into the post groove 32 at the side adjacent to the ring, the

brush being under initial spring tension as above described so that the bend portion presses against the post 3!. The free or contact end of the brush extends from the post along a slight arc that may be concave with respect to the ring so that it lies in the ring groove 2| in a position substantially tangential to the ring in wiping engagement with the ring. As above pointed out the free end of the brush is also under initial spring tension so as to make sufficiently high contact pressure for insuring low contact resistance. With this arrangement the brush 28 runs smoothly in the ring groove 2| regardless of the direction of relative rotation of the brush and ring, and the electrical resistance at the coacting contact surfaces remains substantially constant.

Although I have shown in Fig. 2- the curved contact portion concave with respect to the ring, it will be understood that it may be straight or even convex if desired. For example, the brush and its mounting structure may be positioned above the ring as though the brush terminal portion and associated structure had been rotated 180 about the longitudinal axis of the brush contact portion, in which case the brush contact portion would be convex with respect to the ring.

In addition to being simple, rugged and inexpensive, a particular advantage of the brush arrangement is that it is in efiect self-locking in its mounting, thereby eliminating many common faults of anchoring devices, such as worn-out screw threads in non-metallic supports, and the necessity of replacing an entire multiple unit in case of the failure of a single brush where the brushes are molded in a common support composed of a plastic material, such as an artificial resin. Replacement of an individual brush is easily accomplished because of the resilient construction of the brush and the absence of the usual clamping and fastening devices.

It should be understood that this invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. An electrical slip-ring and brush connection for reversible operation comprising a conducting ring having a peripheral contact surface, a coacting brush for engaging said surface in substantially one-point contact consisting of a strip of resilient conducting material having a portion disposed generally in a direction tangential to the ring periphery and in contact therewith, said strip also having a terminal portion offset from the contact making portion generally in the same plane therewith, and means for anchoring and holding said terminal portion with respect to both transverse and longitudinal movement including a terminal member in which the outer end of said terminal portion is held with respect to transverse movement and a relatively fixed member against which said strip is resiliently biased in a direction away from said ring, said fixed member positioned intermediate said terminal member and contact making portion and engaged by an intermediate part of said strip so as to hold the brush with respect to longitudinal movement whereby a non-chatter relationship'is maintained between said contact portion and ring for rotation of said ring in either direction.

2. An electrical slip-ring and brush connection for reversible operation comprising a conducting ring having a peripheral contact surface forming a groove, a coacting brush consisting of a single conducting wire having a contact portion positioned in said groove so as to lie therein in a direction generally tangential to the ring periphery, said wire also having a terminal portion that is offset with respect to said contact portion generally in the same plane therewith, a terminal member in which said terminal portion is positioned, and a relatively fixed holding member disposed intermediate said terminal member and said contact portion against and on which said wire is biased under initial tension in a direction away from said ring so as to lock said brush in operative position, said wire also being under initial tension for firmly biasing said contact portion transversely into said groove whereby a nonchatter relationship is maintained between said contact portion and ring for rotation'of said ring in either direction.

3. An electrical slip-ring and brush connection for reversible operation comprising a conducting vring having a contact groove at its periphery, a

coacting brush operable in said groove consisting of a single conducting wire of generally scythe shape with a blade-like portion and a terminal portion generally in the same plane, said bladelike portion lying in said groove in a direction generallytangential to the ring periphery and said terminal portion being held against transverse movement at its outer end, and a relatively fixed holding member positioned intermediate the ends of said brush on and against which said wire is biased under initial tension in a directon away from said ring, the configurations of said holding member and a part of said terminal portion being corelated so that said brush is held withirespect to longitudinal movement in interlocked relation to said member.

4. An electrical slip-ring and brush connection for reversible operation comprising a conducting ring having a peripheral contact surface, a coacting brush for engaging said surface consisting of a strip of resilient conducting material having a portion disposed generally in a direction tangential to the ring periphery and in contact therewith at but one place thereof, said strip also having a. terminal portion including a generally U-shaped bend offset from the contact making portion, generally in the same plane therewith, terminal. means for anchoring said terminal portion withrespe'ct to transverse movement, and a relatively fixed post against which said strip is resiliently biased in a direction away from said ring, said post positioned intermediate said terminal means and contact making portion so as to be snugly encompassed in part by said bend thereby holding-said strip with respect to longitudinal movement whereby a non-chatter relationship is maintained between said contact portion and ring for rotation of said ring in either direction.

5, An electrical slip-ring and brush connection for reversible operation comprising a conducting ring having a peripheral contact surface forming a groove, a coacting brush consisting of a conducting wire having a single contact portion positioned in said groove so as to lie therein in a direction generally tangential to the ring periphery,

' said-contact portion being curved with respect to said ring, said wire also having a comparatively straight terminal portion that is oifset with respect to said contact portion generally in the same plane therewith, a terminal member in which the outer end of said terminal portion is anchored against transverse movement, and a relatively fixed post disposed intermediate said terminal member and said contact portion against which said wire is biased under initial tension in a direction away from said ring, said wire being formed so that it partially encompasses said post as it is biased toward the same for resiliently locking said brush in operative position whereby a nonchatter relationship is maintained between said contact portion and ring for rotation of said ring in either direction.

6. An electrical slip-ring and brushconnection for reversible operation comprising a conducting ring having a V-shaped contact groove at its periphery, a coacting brush operable in said groove consisting of a single conducting wire having a curved contact portion and an ofiset terminal portion generally in the same plane, said curved portion being concave with respect to said ring and lying in said groove in a direction generally tangential to the ring periphery and said terminal portion being positioned in a terminal post at its outer end, and a relatively fixed cylindrical memcylindrical member.

7. An electrical slip-ring and brush connection for reversible operation comprising a conducting ring having a contact groove at its periphery, a coacting brush operable in said groove consisting of a single conducting wire of generally scythe shape with a blade-like portion and a terminal portion generally in the same plane, said bladelike portion lying in said groove in a direction generally tangential to the ring periphery and said terminal portion being secured against transverse movement at its outer end, and a relatively fixed holding member located substantially in alinement with said terminal portion, said wire being flexed so that it is positioned at the side of said holding member adjacent to said ring and said terminal portion including a U-shaped bend arranged to fit snugly on said member under initial tension of said wire whereby said brush is .resiliently locked in a non-chatter operative posi- The following references are of record in the file of this patent:

UNITED s'fwras PATENTS Number Name Date 1,480,656 Blackburn Jan. 15, 1924 1,981,854 Comiskey Nov. 27, 1934 FOREIGN PATENTS Number Country I Date 428,099 Great Britain May 7, 1935 

